Mellow Compost Lab

Input Waste Constituents

Here, we share our waste main constituents (greens & browns) coming from different sources; kitchen, garden, woodlands and elsewhere.

There are several elements that are instrumental to making (home) compost: These include waste material (green and brown), moisture (water), air (oxygen) among others: Here we cover the waste material part; what is broadly & commonly known as

  • Greens (also known as Nitrogen-rich components)

  • Browns (also known as Carbon-rich components)

In our home composting lab; our main sources are:


  • Kitchen Waste (KW)
  • Grass clippings
  • Hedge trimmings (mainly Boxwood)
  • Garden waste (GW) - other
  • Coffee grounds (CG)


  • Autumn Leaves (AL)
  • Cardboard (shredded)
  • Sieved compost residue (SR)
  • Small size twigs & sticks
  • Charcoal ground

These constituents in greens and browns are specific to our environment and what we have at our disposal on an annual basis. Of course the list of greens and browns is much larger than this and other home composting might have a different list depending on where they live and have access to.


Grass and Boxwood (hedge trimmings) are also normally classed as garden waste; but they constitute such a large proportion of the overall  garden waste so we felt they deserve a special category each. The other garden waste (GW) from our garden and vegetable plots make up the rest.  Another (optional) green we use is coffee grounds (albeit black in colour); coffee grounds, like grass, are rich in nitrogen and quick releasers. We normally have large supplies by visiting nearby coffee shops and supermarkets.  Usually these latter are not difficult to obtain (except during the 2020-2021 Covid pandemic).

The photo on the left has three buckets, one with grass clippings, one with garden waste and the third one with kitchen waste bin - ready to be shredded and mixed. The photo on the right has typical Boxwood hedge trimming also ready to be shredded. Depending on what is available; we use a powered shredder, a lawn mover or hand-shredded.

Greens shredded & ready
Hedge trimmings before shredding


We measure the proportion of our greens (by volume) that are fed to our compost bins. The pie chart  below shows the long term breakdown since April 2012 to date.  Garden waste in total making up the bulk of the greens (grass, boxwood and the rest of garden waste)  and kitchen waste: 



We collect a large amount of Autumn Leaves (AL) every year, between 23 and 35 bags (of approx 100L  each).  This takes place around end of October to late December in the quiet neighbouring roads and woodlands with large trees and plenty of fallen leaves (typically Sycamore and Beech trees). We use between 15 and 20 bags of AL for compost (browns) and the remaining is used to make leaf mould. 

AL annual collection
Sieved residue
Sieved residue

The image  on the left below is from the 2015 Autumn  leaves collection (23 bags). The sieved residue (SR) comes from sieving raw finished compost (defined as grade III) into grade II. The remaining sieved residue is used for multiple purposes; including back into the waste mix and some also is used for mulching around shrubs. Adding SR into the IW mix helps to create air pockets (oxygen), in particular when mixing dense IW such as grass or shredded hedge leaves. 

Cardboards (cut to bite size) are also an important contributor to the brown material. With the amount of packaged delivery we get nowadays, there is plenty of cardboard and we cut these into bite size (3-4cm cuts). One important note regarding the C:N ratio for cardboard: This latter is significantly higher than AL's, so the mix ratio for greens needs to be proportional. Carboards have a C:N ratio of 350 compared to ALs of 60.